Transformer
A static AC electrical device that transfers electrical energy between circuits through mutual electromagnetic induction to step up or step down AC voltage.
Governing formula
V_s / V_p = N_s / N_p = I_p / I_s
SI unit
Dimensionless (Turns Ratio)
In depth
Step-up transformers increase secondary voltage while decreasing secondary current proportionally. Step-down transformers decrease secondary voltage while increasing current, conserving power (V_p I_p ≈ V_s I_s).
Examples in the real world
Electrical substation transformers stepping up generator voltage to 400,000 V for low-loss long-distance transmission, then stepping down to 120 V for homes.